Remember this? The last time Apple offered a public beta was in 2000. The preview version of the first iteration of OS X came on a disk with a handy how-to guide.

If you're lucky enough to be one of those beta testers, congratulations! Here's a quick rundown of what you should know and keep in mind about the beta as you start poking around Apple's latest operating system. (The final version is due out this fall.)

1. The beta is a work in progress

First and foremost, keep in mind that this isn't the official release of the software; Apple is still testing and tweaking Yosemite. That means it may not function as expected. Some features may be completely absent or could differ from what Apple showed off during its WWDC keynote in June -- and some features may look very different in the final release. Even some of the standard features available in Mavericks or earlier versions of OS X may be missing, nonfunctional or just different. That's because a major OS upgrade, particularly one like Yosemite that makes major changes to the user experience, often involves updating or altering existing functions, including core components that aren't visible to most users.

2. A public beta isn't the same as a developer preview

Apple has already released beta versions of Yosemite to members of its Mac developer program. The most recent was made available to them earlier this week, with revisions arriving roughly every two weeks. In fact, the version of Yosemite offered as the public beta has a different build number (it's one digit higher) than the version developers received on Monday.

Apple's FAQ for the Yosemite beta indicates that beta testers may not see updates at the same rate as developers. There's a good chance this means beta testers will see less frequent updates than developers.

Other differences are likely to include support, resources or some functionality. Developers are receiving the betas to build and/or test apps running under Yosemite and make changes if needed. Beta testers are being asked to provide feedback. Those are rather different roles, and developers aren't likely to provide the type of feedback -- general user interface (UI) issues or consumer-oriented feature requests -- that Apple is looking for from public beta testers.

3. Explore Yosemite and report back to Apple

Apple's goal with this program is largely to solicit feedback about Yosemite, particularly about its new UI. If there are things that aren't working, are confusing, seem like they should work better, or that you really dislike, you should report them to Apple using the Feedback Assistant that's included. During the public beta prior to the release of OS X in 2000, Apple made several changes based on user feedback -- the most obvious was restoring the Apple menu in the shipping version of OS X, which had been replaced with an Apple logo in the middle of the menu bar.

Although Apple suggests simply using your Mac as you normally would, you should also explore a bit. The advantage here for Apple is that you'll play with more Yosemite features and potentially provide more useful feedback. You also might discover new (or existing) features that you might not have considered using otherwise.

You should also report issues with third-party software if it seems that Yosemite has broken something in existing apps. That gives Apple the ability to look at underlying problems affecting those particular apps and potentially others.

4. Don't install Yosemite on a mission-critical Mac

You shouldn't install the Yosemite beta on a Mac that you need for important work. There's a very real possibility that you may encounter a serious problem -- like losing important data, having some key apps stop working or having your entire Mac be disabled.

Let me repeat: Don't install the beta on your primary Mac -- the computer you use day-in and day-out for work or personal tasks. You should install it on a secondary Mac that can easily be wiped clean and restored if need be.

5. You can install Yosemite on an alternate drive or a virtual machine

If you only have one Mac or you decide to ignore my advice and install Yosemite on your primary machine, you should at least consider putting the beta on a drive that isn't your typical startup drive (usually the internal hard drive or SSD inside your Mac). You can install the beta on an external drive, a second internal drive (if your Mac has one), or a hard-drive partition. You can then boot from that drive or partition when you want to use the beta and boot up from your primary startup drive when you need to get things done.

Installation on an alternate drive reduces the risk that a catastrophic failure will befall you or your data, but it isn't a guarantee. An issue that impacts your Mac's file system could affect both the alternate "Yosemite beta" drive and your startup drive. The most likely scenario in this case would be that some type data loss that hits all data on both drives.

Another option, if you have a copy of Parallels Desktop or VMWare Fusion, is to install the Yosemite beta on a virtual machine. Although these tools are typically used to create virtual machines running Windows, they do support other operating systems, including OS X, meaning you can create a virtual Mac and install the Yosemite beta on it. That also reduces -- but doesn't entirely remove -- the risk of problems. If you go this route, you'll want to disable any features that allow the virtual machine to exchange files with your physical Mac to minimize potential data loss if there's a file system issue.

6. Back up any Mac before installing the beta

Whatever Mac you install the Yosemite beta on, and no matter how you install it, you should ensure that you have a complete and functional backup before beginning, even if you are installing on an alternate drive or into a virtual machine. You should also perform regular backups during your testing period. And you should store a known good backup -- disconnected from your Mac -- while testing because a file system issue could damage the data on your backup drive. Ideally, you'll use a second backup drive to perform any regular backups of your Mac while running the Yosemite beta.

7. Think carefully before using iCloud or third-party sync solutions

The risk of data loss isn't restricted to data on your Mac: iCloud data sync among multiple Apple products and third-party cloud services like Dropbox or Google Drive allow your Mac to work with and alter data in the cloud and on other Macs, PCs or mobile devices. You should carefully consider whether you want to risk changes or loss of data maintained or synced through such services. If you decide to use them on a Mac running the beta, you should ensure you have a known good copy of that data separate from the version of the data in the cloud.

Apple explicitly states that documents stored in iCloud will be updated by the Yosemite beta and will only be able to be synced with other Macs running the Yosemite beta (and eventually Yosemite's final release, as well as iOS 8).

Apple exec Craig Federighi announcing Apple's first public beta test for an OS in 14 years. (Image: Apple.)

8. Battery life may be compromised on portable Macs

If you're installing the beta on a laptop, you may notice that power management and battery life don't function normally. This could result in your battery discharging faster than it does when you're running Mavericks or other versions of OS X. This is a common occurrence with operating system betas across platforms. If you are going to be working on the go, you should ensure that you have a power adapter with you, and you may want to observe what, if any, impact the beta has on your MacBook's battery for a day or two after installing it before embarking on any travel.

9. You won't be able to try out Handoff or other Continuity features

Several key Continuity features aren't included. Apple lists phone calls, SMS, Handoff, Instant Hotspot and iCloud Drive as features that aren't fully baked enough to be included in the beta. Several of those require iOS 8, which Apple is not making available in a prerelease state to beta testers (though members of Apple's iOS developer program do have access to preview releases of iOS 8).

10. The beta agreement has confidentiality clauses

Apple is perhaps becoming more open under CEO Tim Cook, but the company still requires some confidentiality regarding unreleased products. The beta-test agreement for Yosemite defines the beta as "Apple confidential information." This means that you are agreeing not to discuss or demonstrate -- in person or online -- your use of the beta, unless you're talking to other beta testers. You can, however, discuss any information that Apple has already made public about Yosemite, since Apple no longer considers information that it has previously disclosed as confidential.

11. Using a Mac that meets the minimum requirements may not mean great performance

Yosemite is designed to run on a range of new and older Macs (the requirements are essentially the same as those for Mavericks and Mountain Lion). The oldest Macs that can run Yosemite include iMacs and MacBook Pros released as far back as 2007. Required specs on supported Macs are 2GB of RAM and 8GB of free storage. This means that you can technically install Yosemite on several older and low-powered Macs.

Your experience, however, is likely to be poor and performance notably slower if you use a Mac that just barely meets the requirements. Although it's difficult to gauge at this point what would be ideal, 4GB is probably the lowest amount of RAM that would enable decent performance (as it is with a Mac running Mavericks). As with most things in computing, the more memory you have, the better.

It's also worth remembering that, as with Mavericks, not all supported Macs have access to all features. AirPlay Mirroring and AirDrop, for example, aren't supported by some older Macs. It's also likely that some of the Continuity features like Handoff in Yosemite won't work on older Macs that lack support for Bluetooth 4/LE.

12. You can revert back to Mavericks if you choose

If you decide that you're not enjoying the process of beta-testing Yosemite, you can revert back to Mavericks. If you've installed Yosemite on an alternate drive, the process is simple -- just reboot from your primary startup drive. If you've installed on your primary drive, you're likely to need to wipe the drive and install Mavericks from scratch or from a backup (another reason to ensure you perform a full backup before installing the Yosemite beta).

13. You should do software updates

Although Apple may be releasing Yosemite updates to beta testers on a different timeline than the one it follows for offering preview releases to developers, the company will almost certainly issue updates during the beta period. You should look for and install these updates, because they will fix known bugs and will likely introduce new features along the way. Once the final build of Yosemite is released, you'll be able to upgrade to it.

The final word: Have fun

A large part of what I've said focuses on the potential pitfalls and problems you could run into while beta-testing Yosemite, along with ways to minimize their impact. You should keep those things in mind, but you should also enjoy testing Apple's latest OS X release. If Apple adheres to its public time frame, we might not be able to do this again until 2028.

Ryan Faas is a freelance writer and technology consultant specializing in Mac and multiplatform network issues. He has been a Computerworld columnist since 2003 and is a frequent contributor to CITEworld.com. Faas is also the author of iPhone for Work (Apress, 2009). You can find out more about him at RyanFaas.com and follow him on Twitter ( @ryanfaas).

Ryan Faas, a contributing writer for Computerworld, is a technology journalist and author who has been writing about Apple, business and enterprise IT topics, and the mobile industry for over a decade.